Queen Elizabeth II longest reign as it happened: Monarch 'touched by messages of kindness' as she overtakes Victoria

Queen Elizabeth II: The life and legacy of Britain\'s longest reigning monarchIBTimes UK

Queen Elizabeth will become Britain's longest serving monarch today when she passes a milestone set by her great-great grandmother Queen Victoria.

The 89-year-old became Queen 63 years and 217 days ago after her father King George VI died in his sleep at approximately 1am on 9 September, 1953. It is estimated she will overtake Victoria at 5.30pm (BST).

Despite the milestone, Buckingham Palace has said the Queen will press ahead with her previously scheduled royal appointments, and along with the Duke of Edinburgh will visit Edinburgh, Midlothian and Tweedbank to officially open the new Scottish Borders Railway.

Over on the Gov.uk website, historian and biographer D R Thorpe has written a post on the Queen's relationship with the 12 prime ministers who lead the country during her reign.

Thorpe writes:

"The central assertion about the rights of a constitutional monarch, as defined by Walter Bagehot in 1867, remains as true as ever: 'the sovereign has under a constitutional monarchy such as ours, three rights – the right to be consulted, the right to encourage, the right to warn.'

While we wait for 5:30pm the time Buckingham Place has down as the official moment when the Queen will overtake her great-great grandmother's reign of 23,226 days, 16 hours and 23 minutes, here are some photos of her down the years.

2 June 1953: Queen Elizabeth II and the Duke of Edinburgh wave to the crowd from the balcony of Buckingham Palace after her coronationAFP

April 1976: The Queen poses for her 50th birthday portrait, in WindsorAFP]

February 1977: Queen Elizabeth II poses for a special Jubilee picture in the Throne Room of Buckingham Palace, after she had delivered the traditional Queen\'s speech at the 1976 official State Opening of Parliament. She wears the Imperial State Crown and the Robe of State. Around her neck is the Jubilee Necklace of diamonds and pearls and the chain is the Collar of the Order of the GarterAFP]

24 May 2011: The Queen holds onto her hat in the wind as she speaks with US President Barack Obama at Buckingham Palace, during his two-day state visitMurray Sanders/Pool

1 September 2012: Prince Philip, the Queen and Prince Charles cheer as competitors participate in a sack race at the Braemar Gathering in ScotlandRussell Cheyne/Reuters

Queen Elizabeth thanked the public for the "touching messages of great kindness" she has received during a rare speech at the opening of the Scottish Borders Railway. She spoke of her gratitude for the messages from home and abroad on.

: The Royal Standard flies from the window of a British Airways jet as it arrives carrying Queen Elizabeth and the Duke of Edinburgh at Joze Pucnik airport on the first day of a two day tour of Slovenia in 2008Getty

Getting into the royal festivities is British Airways. To mark the 63 years since the Queen acceded to the throne the airlines is offering £63 off flights until midnight Wednesday 9 September 2015 - you can browse the long haul destinations here.

In case you missed the Queen's steam powered rail extravaganza earlier today, here's a photo gallery from the journey. After arriving at Waverley station in Edinburgh 40 minutes late due to fog at Balmoral, Queen Elizabeth and the Duke of Edinburgh joined Scotland First Minister Nicola Sturgeon on board the Union of South Africa to Tweedbank, where she unveiled a commemorative plaque.

"The Duke of Edinburgh and I are delighted to be back in the Borders today and especially to have arrived by train. It is wonderful to have witnessed the excitement which the return of the railway has brought here.

We are very grateful for the warmth of your welcome on this occasion. Many, including you, First Minister, have noted another significance attached to today. Although it's not one to which I've aspired. A long life can pass many milestones. Mine is no exception.

I thank you all, and the many others at home and overseas, for your touching messages of great kindness."

While we wait for the Queen to arrive at the Scottish town of Tweedbank, Commonwealth Secretary-General Kamalesh Sharma has praised the monarch on behalf of the 53 countries which were formally part of the British Empire.

Sharma said:

The Queen's personal commitment as Head of the Commonwealth is exemplary, and her devotion to advancing cooperation and understanding continues to inspire people of all ages Commonwealth-wide.

As a symbol of continuity during decades of unprecedented change, and by drawing our people together in their rich diversity, Her Majesty has embodied all that is best in the Commonwealth. With vision and dedication her example has encouraged successive generations of leaders and citizens to embrace the promise of the future.

In congratulating Her Majesty on this historic occasion the Commonwealth joins with a fresh sense of common purpose, committed to advancing in practical ways the shared values and principles now set out in the Commonwealth Charter.

There are now 53 Commonwealth member states, compared to eight when Queen Elizabeth II became Head of the Commonwealth in 1952.

David Cameron is in the House of Commons addressing MPs on the Queen's reign. He says she is a "golden thread" that has run through three post-war generations and she "never falters" when performing duties she enjoys - like attending the Highland Games - or ones she might not, like "spending New Year's Eve in the Millennium Dome". The Queen spent December 1999 at the Dome alongside then prime minister Tony Blair.

THE QUEEN HAS ARRIVED! Along with the Duke of Edinburgh, the Queen arrived at Waverley to cheering crowds waving Union Jack flags. She passed the Royal Company of Archers before boarding the Union of South African steam locomotive for Tweedbank.

The steam locomotive Union of South Africa has arrived at Waverley station before departing with Queen Elizabeth and Prince Philip, Duke of Edinburgh. Accompanying the couple will be Scotland's First Minister Nicola Sturgeon. The Queen will officially open the new Scottish Border's Railway, which runs from the capital to Tweedbank.